808 THE CEINOIDEA CAMERATA OF NORTH AMERICA. 



pieces of the anterior and posterior sides; by this arrangement the piece 

 directed anteriorly is the only radial plate of this ring ; five plates occupy 

 the anal interradius, and the four other sides each have two. The fourth 

 ring has sixteen plates ; some hexangular, others pentangular, five of them 

 radial, the others interradial; of the latter, five occupy the posterior side, 

 one the postero-lateral sides, and two the antero-lateral ones. The fifth 

 ring contains twelve plates, all of which are interradial and arranged in 

 groups of 4, 2, 2, 2, 2. At four sides, the two adjoinhig plates of different 

 interradii meet radially by their lateral angles; but at the posterior side, 

 which has four plates, the two middle ones are separated by plates from the 

 fourth and sixth rings, which meet between them. Of tlie sixth ring, which 

 is followed by the radials, five of the plates are radial, seven interradial; 

 three of the latter occupy the anal side, two the regular sides. There are in 

 all seventy-eight accessory pieces, of which sixteen are radially disposed, the 

 others interradially. The radial plates of the anterior side, and the plates of 

 adjoining interradii together, are arranged exactly like the plates of the 

 posterior side, there being in either case an iininterrupted series of four 

 plates arranged longitudinally, and ten plates to each side ; but, while the 

 one row supports a radial, the other bears an anal plate. The true radials of 

 the species are larger than the plates which support them, wider than high, 

 and hexangidar ; their truncated lower faces rest upon the radial plates of 

 the preceding ring, the lower sloping faces upon the adjoining interradial 

 pieces. The upper faces of the radials are excavated to three fourths their 

 width into a rounded facet similar to that of Plaiycrinus. The anal plate 

 is somewhat longer than the radials, but narrower. 



Horison and Locality. — Coal Measures ; Peoria Co., Ills. 



Type, in the Illinois State collection at Springfield. 



Acrocrimis amptiora W. and Sp. (nov. spec). 

 Plate LXXX. Figs. Jf to 9. 



Smaller than A. Schumardi. Calyx urn-sliaped, more than twice as 

 high as wide, gradually widening from the lower end to the middle, then 

 contracting a little to the top of the radials. The jDlates thin, very slightly 

 convex, and without ornamentation. 



Basals small for the genus, forming a rapidly spreading basin with a 

 shght truncation at the lower end, corresponding to the width of the column. 



